The present disclosure relates to a brushless motor and a rotor.
Japanese Patent No. 4468033 discloses a brushless motor for a variable valve timing apparatus as one example of a conventional motor for a position control apparatus arranged in a vehicle engine room. The brushless motor is provided with a rotor including a rotor core, through which a bore extends in the axial direction, and a field magnet, which is inserted into and fixed to the bore.
In a brushless motor like the one described above, the field magnet is inserted into and fixed to the bore that extends through the rotor core in the axial direction. Thus, the field magnet is easily affected by the ambient environments. For example, when the temperature in the vehicle engine room becomes high, the field magnet is easily demagnetized (irreversible temperature change). When the temperature is high, the magnetic force of the field magnet becomes weak. To cope with this, the current flowing through the coils of a stator may be increased. However, if the current is increased, the field magnet is further easily demagnetized (irreversible temperature change).